Missiles believed to have been fired by a U.S. drone aircraft killed four people in Pakistan’s North Waziristan region on Thursday, hours after a similar strike killed seven in neighbouring South Waziristan.

The drone attacks coincided with the U.S. State Department posting $5 million rewards for information leading to the arrest or location of two al Qaeda allies based in Waziristan.

Two missiles struck a house near the town of Mir Ali in North Waziristan early on Thursday, killing four people, according to Pakistani intelligence officials in the area.

Hours earlier, missiles killed seven people, including four Arab militants in a strike that targeted two vehicles as they drove through the Makeen area of South Waziristan, a stronghold of Pakistani Taliban leader Baitullah Mehsud.

The United States, frustrated by an intensifying insurgency in Afghanistan getting support from the Pakistani side of the border, began launching more drone attacks last year.

It has carried out more than 30 since early 2008, killing about 300 people, including several mid-level al Qaeda members, according to a tally of reports from Pakistani officials, residents and militants.